1. Field of the Invention
The present invention relates to a device for remotely actuating equipment used in relation with pipes though which a fluid flows.
In the oil drilling field, it is often necessary to actuate tools in the drilled well from a distance.
The actuation of such tools requires high powers.
2. Description of the Prior Art
In the prior art, an annular piston was used with two faces and a restriction member comprising a bean system with variable flow section. One face of this piston is subjected to the pressure forces existing on one side of the restriction member, the other face is subjected to the pressure forces existing on the other side of the restriction member.
Generally, the bean is carried by the piston and the needle is fixed relatively to a pipe containing the assembly the piston being movable so as to effect the desired actuation. The piston comprises return means which hold it in an inoperative position corresponding to a relatively high flow section of the restriction member causing a low drop in pressure for service flowrates.
When it is desired to actuate the equipment, the flowrate is increased thereby increasing the pressure drop on each side of the restriction member so that the piston tends to move and runs counter to the return means. In this movement, the bean penetrates more and more into the needle causing a reduction of the flow section of the restriction member whence a greater increase of the drop in the pressure delivering the power for actuating the equipment.
The prior art may be illustrated by the patent FR-2 575 793.
A disadvantage of a device of the aforementioned type resides in the fact that the threshold flowrate is inaccurate thereby causing a tripping of the actuation. In fact, the assembly formed by the piston and the return spring, which must react to or transmit high powers, cannot respond accurately to a given flowrate threshold due to, for example, the friction forces.